The use of viable microorganisms as root-zone inoculants, particularly beneficial bacteria, has expanded to include many food crops including fruits, vegetables, root crops and grains. The emerging science, referred to as probiotics, is based in part on the observation that certain soils, which contain specific cultures of microorganisms that aggressively colonize root surfaces, suppress a variety of plant diseases. It is postulated that colonization of root surfaces with deleterious microorganisms can be prevented by pre-colonization with probiotic microorganisms, which is referred to as competitive exclusion (CE). Schroth, et al. (1982) entitled “Disease-Suppressive Soil and Root-Colonizing Bacteria”, Science, Vol. 216: 1376-1381 (1982). In this review, gram-negative Pseudomonas bacterial species were discussed as being the most effective in CE, and their ability to produce iron-binding compounds (called “siderophores”) was postulated as the potential mode-of-action.
U.S. Pat. No. 5,503,651 discusses plant growth promoting rhizobacteria (referred to therein as “PGPR”), and in a listing of 41 PGPR bacterial species, 37 of them are Pseudomonas species and strains. Since strains of these same Pseudomonas species are plant pathogens, and since plasmid transfer within a bacterial species is commonplace, there is a concern that there could be transfer of genetic material from a pathogenic strain, to convert a previously harmless strain into a pathogenic strain. Accordingly, it is preferred to use gram-positive bacteria, such as Bacillus, and not gram-negative Pseudomonas, for probiotics.
U.S. Pat. No. 4,877,738 discusses a seed inoculum for application to seeds to be protected from “damping off” fungal plant disease, and this patent also discusses a method of protecting growing plants from damping off and root rot fungal plant disease with a similar composition. The composition includes a carrier and an effective quantity of protective bacteria, including Bacillus cereus ATCC 53522, a mutant of Bacillus cereus ATCC 53522 retaining the capability to produce a plant protecting toxin effective against Phytophthora megasperma, a mixture of such mutants, and a mixture of Bacillus cereus ATCC 53522 and such mutants wherein the inoculum is substantially soil-free. There is no indication that testing of any other Bacillus species for such purposes had the same effect.
U.S. Pat. No. 4,952,229 discusses a microbial plant supplement and method for increasing plant productivity and quality, which includes a mixture of microbes with various in vivo properties. This patent also states that the microbes should be used with certain organic acids, and with trace metals and minerals.
U.S. Pat. No. 4,952,229 describes commercialization hurdles for mixtures of microbial strains, because it would be difficult and expensive to insure uniform end-products due to the difficulties associated with consistently combining a plurality of microorganisms. Without a consistent and uniform end-product, it would be difficult to obtain the regulatory permits required for sales and marketing of such products. It is indicated to be preferable for a single strain of a single species is the only active ingredient in a commercial product.
U.S. Pat. No. 5,441,735 discusses the use of the microorganism Erwina carotovora subsp. carotovora (E234M403 strain) which has been modified by mutagenesis to eliminate its soft rot pathology in rice. When applied to rice plants, this modified strain competitively excludes pathogenic strains of the same species. The disadvantage with this strain is the same as discussed above with Pseudomonas, i.e., a reversion to pathology is possible since this microorganism is pathogenic prior to mutation. Also, it is clear that this microorganism is of no benefit to rice that is not experiencing a soft rot infection.
U.S. Pat. No. 5,157,207 discusses a method of inoculating bacteria into rice by introducing a bacterial cell into the seed or plant, such bacteria belonging to the species Calvibacter xyli. This creates a modified rice plant that demonstrates a slight yield improvement (4.81 kg/ha treated vs. 4.66 kg/ha control). Microbial invasion into rice plant tissue is not preferred, however, as it raises possible health and regulatory concerns.
There is a need for new enhancing yields in rice farming beyond those achieved with modern “high yielding” rice varieties. From 1964 to 1990, irrigated rice field yields in Asia increased from 3.0 to 5.8 metric tons/ha. This was largely the result of the introduction of the higher yielding IR varieties of rice developed by the International Rice Research Institute in the Philippines, starting with IR-8 in 1966. At the time of introduction, IR-8 yielded 10 metric tons/ha in the Philippines and up to 14 metric tons/ha in certain temperate regions of China, where fewer overcast days resulted in enhanced photosynthesis. Yields from variety IR-8, as well as other IR varieties, have decreased at a rate of 0.2 metric tons/ha/yr. Pingali, et al., C.A.B. International & International Rice Research Institute (1997), “Asian rice bowls: The returning crisis?” New York: CAB International. Yields of 6 metric tons/ha are seldom achieved by Asian farmers. New rice varieties are being selected more for disease resistance, shorter photoperiod, and grain quality than for yield. It has become generally accepted within the industry that yield increases from advances in plant genetics have been effectively maximized, and further increases can only be achieved by other means. A similar need exists for other crops due to pressures on the environment and increased demand for food production.
Tomato-Tone® (plant fertilizer) made by Esporma comprises a fertilizer and Bacillus species bacteria for use as an organic fertilizer. Serenade® Garden Disease Control (anti-fungal spray for plants) contains Bacillus subtilis, a soil-dwelling bacterium that controls leaf blight, black mold, powdery mildew and many other diseases. However, both products contain relatively low amounts of Bacillus and are designed for small-scale use.
Serenade® (microbial control agent) is a microbial biological control agent comprising Bacillus subtilis strain QST 713 which protects against fungal and bacterial plant pathogens. Bacillus subtilis strain QST 713 is a naturally occurring widespread bacterium that can be used to control plant diseases including blight, scab, gray mold, and several types of mildew. SERENADE SOIL® (biofungicide) is a fungicide designed to protect young plants against the effects of soil diseases like Pythium, Rhizoctonia, Fusarium and Phytophthora. 
Annual crop losses due to pre- and post-harvest fungal diseases exceed $260 Billion annually. About 15,000 fungal species cause disease in plants. The majority of these fungal plant pathogens belong to the Ascomycetes and Basidiomycetes. González-Fernandez, et al. Journal of Biomedicine and Biotechnology Vol. 2010, Article ID 932527, 26 pages, 2010. Plant pathogens can have many devastating effects on a variety of commercial crops. Thus there exists in the art a need for compositions and methods for controlling plant fungal pathogens.